The present invention is with respect to a fastener for forcing together and fastening together at least two structures having lined-up holes, with a fastener head which is greater in size than the holes and having a shoulder facing the structures for resting against the outer face thereof, and a stem which is coaxial to the head and made in one piece therewith, the stem stretching out from the shoulder on the head and having an outline in agreement with the form of the holes in the structures to be fastened. By way of a gripping keeper, which has a working face turned towards the shoulder, the two structures may be fastened and kept together. As used in this specification, the term, "structures" which are fastened together is intended to mean members of any sort, which are capable of being fastened together by the invention.
In the prior art (see for example U.S. Pat. No. 3,923,326, FIG. 3) two corner pieces may be joined together by a fastening system which is furthermore used for pulling the two corner pieces together when the join is being made between them. The corner pieces have, in their outer corner parts, in-line holes 44 which, in the patent, are round. The stem of a screw is slipped through such a hole so that the screw's head 69 comes to rest against the outer side of the one corner piece. On the outer side of the other corner, a nut washer is placed and then a nut is screwed on the part of the screw stem stretching out through the hole. With the help of two spanners, the join is then done up tight. Because of nosepieces 64 and 68 acting as fulcrums, the legs 41 and 42 of the corner pieces 39 and 46 are pulled together. Such a system has, however, a number of undesired effects and properties, namely:
(a) Two spanners are needed, one for the nut and the other for the screw or bolt head.
(b) For each different size of screw and nut, a different size of spanner is needed.
(c) Three separate parts are needed in each case, that is to say the screw or bolt, the washer and the nut.
(d) Because the three parts are not permanently joined together, any one of them may be lost before fastening.
(e) Although all three parts are mass produced, there is a certain lower price limit, because male and female threads have to be cut and making hex heads is a highprice operation as well.
(f) Tight size limits have to be kept to as otherwise the parts may not be turned and done up tight with the spanners or the threads will become jammed or will have overmuch play. This side of fastener design is covered by a mass of industrial standards in many manufacturing countries.
(g) Of the threaded length of the stem, only a very small part is used for the nut and the rest of the thread cut is not used, but nevertheless has to be produced at a high price.
(h) The force is only taken up by the sides of the thread facing the structures fastened and the force only goes by way of the roots of the thread to the stem.
(i) On attempting to put on the nuts, it is readily possible to get them cross-threaded so that the first part of the thread may be stripped.
(j) Three different sorts of parts have to be warehoused which, for assembly, have to be put together in the right way.
(k) Frequently there is not enough space for turning the spanners.
(l) For turning a nut right round through one complete turn, the spanner has to be put on it and taken off it again at least twice, more commonly, however, five to ten times.
(m) If the fastener is to be undone, the same complex operation is necessary doing things in the opposite order.
(n) If the screws are used for keeping the holes, and the parts in which they are made, in line, such parts will only be supported on the tops of the thread on the screw and not over a large face, so that damage to the screw is likely.
(o) The height of the screw head and, furthermore, of the nut is made larger than is necessary for taking up the forces in question. In fact, the height, and, for this reason, the use of further material, of the heads and nuts is necessary so that they may be gripped with the spanners.
(p) If such fasteners are to be put in place in a works, power spanners are generally used to make the best use of man power. Such power spanners are, however, high in price and are very loud in operation. Furthermore, their electric cables may be cut at the sharp edges of sheet metal structures. If such fasteners are to be put in place on a building site, a special electric supply system has to be fixed up.